Skip to main content

Full text of "IS 12967-1: Analysis of hydraulic transients in hydro-electric and pumping plants - Code of practice, Part 1: Criteria for analysis"

See other formats




Wtt * 

Disclosure to Promote the Right To Information 

Whereas the Parliament of India has set out to provide a practical regime of right to 
information for citizens to secure access to information under the control of public authorities, 
in order to promote transparency and accountability in the working of every public authority, 
and whereas the attached publication of the Bureau of Indian Standards is of particular interest 
to the public, particularly disadvantaged communities and those engaged in the pursuit of 
education and knowledge, the attached public safety standard is made available to promote the 
timely dissemination of this information in an accurate manner to the public. 

Mazdoor Kisan Shakti Sangathan 
"The Right to Information, The Right to Live' 

" T T/U^ # #g" ?& % ^V%" 

Jawaharlal Nehru 

'Step Out From the Old to the New' 

IS 12967-1 (1990) : Analysis of hydraulic transients in 
hydro-electric and pumping plants - Code of practice, Part 
1: Criteria for analysis [WRD 14: Water Conductor Systems] 




bK^f J f JlA^s^fe^rs^^il TY^>^ 

;SSMV H>ft5!>5^N5^> 


Satyanarayan Gangaram Pitroda 
Invent a New India Using Knowledge 

fTR" Tt^t f^TT <sMHI | ^ ^pfT ^^FTT ^ W *TWT If 

Bhartrhari — Nitisatakam 
"Knowledge is such a treasure which cannot be stolen" 




IS 12967 ( Part 1 ) : 1990 

~ ( Reaffirmed 2001 ) 

areata *THaf5 

vrm l fa^OT % mq^s 

Indian Standard 





UDC 627-844 : 620 , 162"4 : 621311*21 

© BIS 1991 


NEW DELHI 110002 

January 1991 Price Group 2 

Water Conductor Systems Sectional Committee, RVD 14 


This Indian Standard was adopted by the Bureau of Indian Standards on 20 March 1990, after 
the draft finalized by the Water Conductor Systems Sectional Committee had been approved by 
the River Valley Projects Division Council. 

The hydraulic transients are caused due to unsteady discharges resulting from operation of 
hydroelectric and pumping plants. The hydraulic transients may be caused both during normal 
or emergency conditions of operation. There are various devices to reduce or eliminate 
undesirable transients and it shall be selected after careful study of different alternatives. 

IS 12967 ( Part 1 ) : 1990 

Indian Standard 






1.1 This code deals with the hydraulic transient 
in closed conduits of a Hydro-Electric Plant 
and discharge line of pumping plant. 


2.0 For the purpose of this standard the follow- 
ing definition shall apply. 

2.1 Hydraulic Transient 

In a closed conduit, when the flow is unsteady 
that is the discharge at each section is varying 
rapidly from one instant to the next, rapid 
pressure changes occur inside the conduit. 
Such pressure changes caused by rapid flow 
changes are termed as hydraulic transient. 


3.1 Turbine — Penstock Installation 

The following operations produce transient 
conditions in a turbine penstock installation: 

a) Unit Synchronized to a Large System 
i) Load acceptance 

ii) Load reduction or total load rejection 

b) Isolated Unit 

i) Unit start up 
ii) Load acceptance 
iii) Load reduction or total load rejection 

c) Hydraulic transients produced by 
resonance due to the vibration of runner 
blade and guide vanes, leakage from valve 
seal and governor hunting. 

3.2 Pumping Installation 

The following operations produce transient 
state conditions in the discharge line of 
pumping installations: 

a) Opening, closing or chattering of valves in 
a pipe-line; 

b) Starting and stopping the pumps in a 
pumping system; 

c) Stoppage of pumps due to sudden power 
failure; and 

d) Resonance caused by leakage from valves, 
vibration of guide vanes. 


4.1 For calculation of hydraulic transient in a 
turbine penstock installation and pumping 
installation, data required is as follows: 

a) Turbine Penstock Installations 

i) Details of water conductor system such 
as profile length, shape, material of 
conduit and size of conduits; 

ii) Type, location and characteristics of 
protective devices such as surge tank 
and pressure relief valves; 

iii) Type of turbine and turbine 

iv) Generator characteristics like torque, 
inertia and efficiency; 

v) Type of governor and its characteristics; 

vi) Design discharge and head on turbine. 

b) Pumping Installation 

i) Details of discharge line, such as, profile, 
length, shape and size of pipe line 
including location; 

ii) Type, location and characteristics of 
protection devices on pipe line such as 
surge tanks, air chamber, valves, etc; 

iii) Pump characteristics; and 

iv) Design discharge and pumping head. 


5.1 Following are some of the constraints set by 
operational requirements for the calculation of 
hydraulic transients in turbine-penstock 
installation and pumping installation. * 


IS 12967 ( Part 1 ) : 1990 

5.2 Turbine — Penstock Installation 

5.2.1 The maximum reduction in electrical 
power output that can result from circuit 
breaker operation. 

5.2.2 The maximum allowable speed rise in the 
turbine fed by any one penstock. 

5.2.3 The maximum rates of load change that 
generating plant is required to accommodate to 
satisfy system requirements. 

5.2.4 Limitations set over the range of variation 
of transient pressures. 

5.3 Pumping Installation 

5.3.1 The maximum reduction in power input 
that can result from electrical faults. 

5.3.2 Limitation set on the magnitude and rate 
of variation of discharge. 

5.3.3 Limitation set on reverse rotation of 

d) Unless the actual turbine characteristics 
are known the effective flow area through 
the turbine gates or nozzles during 
maximum rate of gate movement may be 
assumed to be linear with respect to 

e) The turbine gates may be moved at any 
rate of travel by the action of the 
governor head up to a predetermined rate 
or at a slower rate by manual control 
through auxiliary relays. The water 
hammer effects may be computed on the 
basis of governor rate which is set by the 
governor relay valve stops for speed 

f) The penstock alignment shall be checked 
such that due to load acceptance water 
column separation shall not cause a 
penstock failure due to collapse; and 

g) When the closure is set at a slow rate, the 
water hammer caused by runaway when 
full load discharge reduces to runaway 
discharge during the speed rise shall be 

5.3.4 Limitation set on the 
column separation in pipe lines. 


6.1 The pressure rise due to hydraulic transient 
conditions in a turbine penstock installations 
and pumping installations are considered for 
the following conditions. 

6.2 Turbine — Penstock Installation 

6.2.1 Normal Operating Condition 

The design criteria for dynamic pressure rise or 
drop due to water hammer under normal 
operating conditions shall be due to full load 
rejection or specified acceptance. The basic 
conditions to be considered as normal operations 
are as follows: 

a) The turbine-penstock installation may be 
operated at any head between the 
maximum and minimum water levels in 
the reservoir or forebay or surge tank; 

b) The turbines may be operating at any 
gate position and be required to drop any 
or all of the load; 

c) Where the turbine-penstock installation is 
equipped with any of the pressure control 
devices like surge tanks, relief valves, 
governor control device and cushioning 
stroke device, it is assumed that these 
devices are properly adjusted and function 
in the manner as contemplated in the 

formation of 6.1.2 Emergency Condition of Operation 

For emergency condition of operation the 
dynamic pressure rise is due to sudden load 
rejection. The basic conditions to be considered 
as emergency operation for an impulse and 
reaction turbine is as follows: 

a) Impulse turbine 

The dynamic pressure rise due to 
needle slam on loss of oil pressure or 
mechanical failure. As the needles are 
hydraulically balanced at mid-point, 
the turbine flow cut-off shall be taken 
as instantaneous due to slam closure of 
of the needles from half position. 

b) Reaction turbine 

i) The turbine gates may be closed at any 
time by the action of the governor 
head, manual control of the main relay 
valve or by the emergency selenoid 
device. The gate traversing time will 
be taken as the minimum time for 
which the governor is designed; 

ii) Cushioning stroke or pressure relief 
valve if present, shall be assumed to be 
inoperative in one unit; and 

iii) The water hammer shall be computed 
for the maximum reservoir head 
condition for final part gate closure to 
zero gate position on one unit at the 

maximum governor rate of — —seconds. 

IS 12967 { Part 1 ) : 1990 

6.2 Pumping Installation 

6.2.1 Normal Conditions of Operation 

i) Pumps may be started or tripped 
manually or automatically throughout 
the entire range of pumping heads 
specified for the installation; 

ii) If there is more than one pump on the 
line, all are tripped simultaneously, 
however, only one may be started; 

iii) Where the pump discharge system is 
equipped with any of the pressure 
control devices like surge tanks, air 

iv) Ii" a check valve is present in the 
discharge line, the hydraulic transients 
will be computed on the basis that the 
check valves close immediately upon 
the reversal of flow; 

v) If an air chamber is present in the 
pump discharge line system, it is 
assumed to have a minimum air 
volume during the power failure; and 

vi) The alignment of the pump discharge 
line shall be checked to see that water 
column separation does not occur at 
any point, due to power failure. 

6.2.2 Emergency Conditions of Operation 

i) If surge suppressors, surge tanks or 
pressure relief valves are present only 
one will be assumed to be inoperative; 

ii) Closure of one of the check valves 
provided for shutting off return flow 
through the pumps is delayed and 
occurs at the time of maximum reverse 

iii) Air-inlet valves, if present in the system 
are assumed to be inoperative; and 

iv) Power failure occurs at any time 
during or following the starting of a 
pump or pumps. 


7.1 Turbine-Penstock Installation 

The minimum factor of safety to be adopted 
for the design of turbine penstock, surge tank 
and other pressure control devices to withstand 
normal and emergency condition of operation 

shall be as follows: 
Conditions of Operation 

a) Normal ( one unit ) 

b) Normal ( more than 
one unit ) 

c) Emergency 

Factor of Safety 



7.2 The factor of safety is based on the yield 
point stress of steel pipe lines, turbine or pump 
casing. The factor of safety for specials like 
bifurcation is increased by 125 percent. 


8.1 The devices commonly used to reduce or to 
eliminate the undesirable transients such as 
excessive pressure, column separation and 
pump or turbine over speed following a power 
failure or load rejection are following: 

i) Surge tanks; 

ii) Air chamber; and 

iii) Valves such as safety valves, pressure 
relief valve, pressure regulating valve, air 
inlet valves, check valves and bursting disc. 

8.2 Surge tank and pressure relief valves are 
used on a turbine penstock installation to 
control pressure rise due to hydraulic transient. 
On a pumping installation all the devices 
mentioned above are used together or in 

8.3 The severity of undesirable transients can 
also be reduced by any of the following 

a) By changing profile of pipeline; 

b) By increasing diameter of pipeline; 

c) By reducing water hammer wave velocity; 

d) Use of check valves downstream of 

NOTE — Wave velocity depends on elastic 
parameters and also conduit size, wall thickness 
and wall material and also external constraints 
such as type of support and freedom of 
longitudinal movement of conduit. 

e) The rotation inertia of turbine or pump 
and of generator or motor mechanically 
coupled to turbine or pumps. 

f) Dual closing of guidance servomotors. 

8.4 The choice and type of controlling devices 
to be used shall be decided by various 
alternative studies. The alternative that gives 
an acceptable system response as defined by 
operation requirement and overall economical 
system shall be selected. 

Standard Mark 

The use of the Standard Mark is governed by the provisions of the Bureau of Indian Standards 
Act, 1986 and the Rules and Regulations made thereunder. The Standard Mark on products 
covered by an Indian Standard conveys the assurance that they have been produced to comply with 
the requirements of that standard under a well defined system of inspection, testing and quality 
control which is devised and supervised by BIS and operated by the producer. Standard marked 
products are also continuously checked by BIS for conformity to that standard as a further safe- 
guard. Details of conditions under which a licence for the use of the Standard Mark may be granted 
to manufacturers or producers may be obtained from the Bureau of Indian Standards. 

Bnrsan of Indian Standards 

BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promote 
harmonious development of the activities of standardization, marking and quality certification 
of goods and attending to connected matters in the country. 


BIS has the copyright of all its publications. No part of these publications may be reproduced in 
any form without the prior permission in writing of BIS. This does not preclude the free use, in 
the course of implementing the standard, of necessary details, such as symbols and sizes, type or 
grade designations. Enquiries relating to copyright be addressed to the Director ( Publications ), 

Revision of Indian Standards 

Indian Standards are reviewed periodically and revised, when necessary and amendments, if any, 
are issued from time to time. Users of Indian Standards should ascertain that they are in 
possession of the latest amendments or edition. Comments on this Indian Standard may be sent 
to BIS giving the following reference: 

Doc : No RVD 14 ( 4660 ) 

Amendments Issned Sines Publication 

Amend No. Date of Issue Text Affected 



Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002 

Telephones : 331 01 31, 331 13 75 Telegrams : Manaksanstha 

( Common to all Offices ) 

Regional Offices: 

Central : Manak Bhavan, 9 Bahadur Shah Zafar Marg f33l 01 31 

NEW DELHI 110002 1331 13 75 

Eastern : 1/14 C.I.T. Scheme VII M, V.I.P. Road, Maniktola 37 86 62 

CALCUTTA 700054 

Northern : SCO 445-446, Sector 35-C, CHANDIGARH 160036 2 18 43 

Southern : C.I.T. Campus, IV Cross Road, MADRAS 600113 41 29 16 

Western : Manakalaya, E9 MIDC, Marol, Andheri (East) 6 32 92 95 

BOMBAY 400093 


Printed at Arcee Preii, New Delhi. India